Karst engineering studies at the Akköprü Reservoir area, southwest of Turkey

Akköprü Dam, which is under construction, is located at Dalaman Basin in the southwest of Turkey. The base rock at the Akköprü dam site and reservoir area is autochthon Akta? limestone and Gökseki flysch formation. Allochthon Cehennem Deresi limestone, a complex series of ferro- (melange) and peridotite–serpentine units, overlay this unit with tectonic contact. These units are covered by young sedimentary series. The outcrops of karstified Akta? limestone are observed at 2 km upstream of the dam site, at the right reservoir abutment. This unit is very permeable and the groundwater level is very deep, 100–116 m below the Dalaman riverbed. After impoundment, 250,000 m² of this unit will be submerged. Groundwater which percolates in this unit discharges at the coastal springs. This study analyzed the watertightness of Akköprü reservoir related to the karstified limestone in the left reservoir bank and discussed possible options of remedial works to reduce seepage.     

Assessment of Relationship Between Grouted Values and Calculated Values in the Bazoft Dam Site

Seepage through foundation and abutments of a dam can potentially result in a waste of the water stored in dam reservoir, erosion of foundation materials, and development of uplift pressure in dam foundation which, consequently, threatens the long-term stability of the dam. In this study, the grout volume is estimated based on parameters such as joint aperture, the maximum penetration length of the grout, and calculated grout take in Bazoft dam site. Bazoft Dam is a hydroelectric supply and double-curvature arch dam with a height of 211 m located in Chaharmahal and Bakhtiari Province of Iran. The bedrock of Bazoft dam site consists of Asemari Formation (limy marl and marly lime), in the middle and upper parts of left abutment, and Jahrom Formation (limestone and dolomite) in the right abutment, river bed, and lower part of left abutment. The joint apertures were calculated based on the permeability and the joint spacing. Next, the maximum penetration length of the grout and grout volume were calculated. Using a statistical analysis, the relationship of the joint aperture, maximum penetration length, and the calculated grout volume with real grout take was also investigated. The results show that the grout take can be predicted with appropriate accuracy based on the calculated grout volume.     

Seepage problems in the karstic limestone foundation of the Kalecik Dam (south Turkey)

Seepage phenomena through the karstic limestone foundation of Kalecik Dam are investigated. The dam, designed as a rock-fill dam with a height of 77 m, is already used for irrigation. The foundation consists of Mesozoic ophiolite, Paleocene allochthonous units composed of different lithologies, and Miocene conglomerate. The conglomerate lies unconformably on the other units. Quaternary basaltic lava patchily covers the others. Seepage from upstream to downstream occurs through the allochthonous karstic limestone. This limestone, which is overlain by conglomerates, has a thickness increasing towards the right abutment.

To prevent seepage at the right abutment, a 200-m long and 60-m deep grout curtain along the dam axis was constructed. After the impoundment, some springs occurred downstream, and for this reason, extra grouting was performed. However, the seepage problem could not be solved. In order to determine the seepage direction and karstification pattern, hydrological studies have been done. Additional investigation boreholes have been drilled to observe fluctuations of the groundwater level and to analyze hydrochemistry. Also, dye tracer tests have been carried out.

As a result of these hydrogeological studies, seepage paths were observed in the karstic limestone located between the dam and the spillway. As those carbonate rocks continue beneath the spillway, the seepage problems are enjected to continue.     

Re-evaluation of the Cablac Limestone at its type area, East Timor: Revision of the Miocene stratigraphy of Timor

The Cablac Limestone, widely recorded in Timor, has its type area on Cablac Mountain where it was regarded as a Lower Miocene shallow-marine carbonate-platform succession. The Bahaman-like facies placed in the Cablac Limestone are now known to belong to the Upper Triassic–Lower Jurassic rather than the Lower Miocene. On the northern slopes of Cablac Mountain, a crush breccia, formerly regarded as the basal conglomerate of the formation, is now considered to have developed along a high-angle fault separating Banda Terrane units of Asian affinity from an overthrust limestone stack containing units belonging to the Gondwana and Australian-Margin Megasequences. The Cablac breccia includes rock fragments that were probably derived locally from these tectonostratigraphic units after terrane emplacement and overthrusting. Clasts include peloid and oolitic limestones of the Upper Triassic–Lower Jurassic derived from the Gondwana Megasequence, deep-water carbonate pelagites of the Cretaceous and Paleogene derived from the Australian-Margin Megasequence, Upper Oligocene–Lower Miocene (Te Letter Stage) shallow-water limestone derived from the Banda Terrane, and a younger Neogene calcarenite containing clasts of mixed tectonostratigraphic affinity. There is no evidence for significant sedimentary or tectonic transport of clasts that form the breccia. The clast types and the present understanding of the geological history of Timor suggest that the crush breccia formed late in the Plio-Pleistocene uplift history of Timor. It is not the basal conglomerate of the Cablac Limestone. However, the clasts of an Upper Oligocene–Lower Miocene limestone found in the breccia suggest that a shallow-marine limestone unit of this age either outcrops in the region and has not been detected in the field, or has been eroded completely during late Neogene uplift. The clasts are similar in age and lithology to an Upper Oligocene–Lower Miocene formation that unconformably overlies a metamorphic complex in the Booi region of West Timor, similar to the Lolotoi Metamorphic Complex (Banda Terrane) that is juxtaposed against the crush breccia of Cablac Mountain. The Cablac Limestone at its type area includes a mixed assemblage of carbonate rock units ranging in age from Triassic to Plio-Pleistocene and representing diverse facies. As a formation, the name “Cablac Limestone” should be discarded for a Cenozoic unit. The Upper Oligocene–Lower Miocene shallow-water limestone unit that is typified by outcrops in the Booi region of West Timor, and that has contributed to clasts in the Cablac breccia, is informally named the Booi limestone. It is considered part of the allochthonous Banda Terrane of Asian affinity and represents the only shallow-marine Lower Miocene unit known from Timor. The only other Miocene sedimentary unit known from Timor includes carbonate pelagites – designated the Kolbano beds – probably deposited on an Australian continental terrace at water depths between 1000 and 3000 m. On the northeastern edge of Cablac Mountain, oolitic limestone and associated units of the Gondwana Megasequence, the Kolbano beds of the Australian-Margin Megasequence, and the Booi limestone and associated metasediments of the Banda Terrane were juxtaposed by a Plio-Pleistocene high-angle fault along which the Cablac crush breccia formed.     

Re-evaluation of the Cablac Limestone at its type area,East Timor: Revision of the Miocene stratigraphy of Timor

The Cablac Limestone, widely recorded in Timor, has its type area on Cablac Mountain where it was regarded as a Lower Miocene shallow-marine carbonate-platform succession. The Bahaman-like facies placed in the Cablac Limestone are now known to belong to the Upper Triassic–Lower Jurassic rather than the Lower Miocene. On the northern slopes of Cablac Mountain, a crush breccia, formerly regarded as the basal conglomerate of the formation, is now considered to have developed along a high-angle fault separating Banda Terrane units of Asian affinity from an overthrust limestone stack containing units belonging to the Gondwana and Australian-Margin Megasequences. The Cablac breccia includes rock fragments that were probably derived locally from these tectonostratigraphic units after terrane emplacement and overthrusting. Clasts include peloid and oolitic limestones of the Upper Triassic–Lower Jurassic derived from the Gondwana Megasequence, deep-water carbonate pelagites of the Cretaceous and Paleogene derived from the Australian-Margin Megasequence, Upper Oligocene–Lower Miocene (Te Letter Stage) shallow-water limestone derived from the Banda Terrane, and a younger Neogene calcarenite containing clasts of mixed tectonostratigraphic affinity. There is no evidence for significant sedimentary or tectonic transport of clasts that form the breccia. The clast types and the present understanding of the geological history of Timor suggest that the crush breccia formed late in the Plio-Pleistocene uplift history of Timor. It is not the basal conglomerate of the Cablac Limestone. However, the clasts of an Upper Oligocene–Lower Miocene limestone found in the breccia suggest that a shallow-marine limestone unit of this age either outcrops in the region and has not been detected in the field, or has been eroded completely during late Neogene uplift. The clasts are similar in age and lithology to an Upper Oligocene–Lower Miocene formation that unconformably overlies a metamorphic complex in the Booi region of West Timor, similar to the Lolotoi Metamorphic Complex (Banda Terrane) that is juxtaposed against the crush breccia of Cablac Mountain. The Cablac Limestone at its type area includes a mixed assemblage of carbonate rock units ranging in age from Triassic to Plio-Pleistocene and representing diverse facies. As a formation, the name “Cablac Limestone” should be discarded for a Cenozoic unit. The Upper Oligocene–Lower Miocene shallow-water limestone unit that is typified by outcrops in the Booi region of West Timor, and that has contributed to clasts in the Cablac breccia, is informally named the Booi limestone. It is considered part of the allochthonous Banda Terrane of Asian affinity and represents the only shallow-marine Lower Miocene unit known from Timor. The only other Miocene sedimentary unit known from Timor includes carbonate pelagites – designated the Kolbano beds – probably deposited on an Australian continental terrace at water depths between 1000 and 3000 m. On the northeastern edge of Cablac Mountain, oolitic limestone and associated units of the Gondwana Megasequence, the Kolbano beds of the Australian-Margin Megasequence, and the Booi limestone and associated metasediments of the Banda Terrane were juxtaposed by a Plio-Pleistocene high-angle fault along which the Cablac crush breccia formed.     

文山小河尾水库岩溶渗漏水文地质条件与管道位置识别

小河尾水库是云南省文山州重要的集中式饮用水水源地,承担着22万人饮水供应任务,长年受到渗漏病害问题困扰。文章在水文地质调查基础上,提出小河尾水库岩溶渗漏水文地质条件的新认识:泥盆系坡折落组硅质岩和榴江组硅质岩构成南北两侧隔水边界,中间厚约40米的分水岭组灰岩构成渗漏条带,一NE-SW向压扭性逆断层F₁构成西侧隔水边界,库水主要向东北侧渗漏。采用大功率充电法和音频大地电磁法2种物探方法探测岩溶渗漏管道位置和深度,并实施钻孔验证,综合分析水文地质调查、物探和钻探成果,认为在分水岭组灰岩与上部榴江组硅质岩、下部坡折落组硅质岩岩性接触带附近分别存在强岩溶渗漏带,并分析2处强岩溶渗漏带分布特征、规模和充填性质,为小河尾水库渗漏治理提供依据,为以后岩溶地区类似水库渗漏病害问题调查治理提供借鉴。      

The Lar Dam; an example of infrastructural development in a geologically active karstic region

The problems associated with the construction of the Lar Dam, Iran, provide a classic example of problems that can result from infrastructural development in an active geological terrain which includes the regional carbonate units. The Lar Dam lies in a heavily faulted and fractured region close to the active Damavand volcano. The fracturing has enhanced the production of karst and sinkholes in the limestone below the dam, and acidic ground-water run-off from the Damavand volcano increases the dissolution of the carbonate beds along the fractures to produce sinkholes below the dam. The initial problem of building the dam in such a region is compounded by the relationship between water loss due to enhanced sinkhole development and the remedial measures being taken to lessen this leakage. Drainage of the sub-reservoir caverns through leakage along fractures can lead to loss of hydrostatic support for the developing sub-reservoir caverns, and their consequent collapse. Furthermore, rapid changes in subterranean water levels would lead to rock-shattering hammer effects particularly during rapid rises in water level.     

Sediment changes upstream and downstream of the Altnahinch Dam in the River Bush in Northern Ireland: a preliminary study

The River Bush must reach a standard of good ecological potential (GEP) by 2015 due to the requirements of the water framework directive. The role of sediments within a water body is extremely important to all aspects of a river’s regime. The aim of this research is to investigate the effects of Altnahinch Dam on sediment distribution in the River Bush (a heavily modified water body) with comparison made against the Glendun River (an unmodified water body). Samples collected from the rivers were analysed by physical (pebble count, sieve analysis) and statistical methods (ANOVA, GRADISTAT). An increase in fine sediments upstream of the dam provides evidence that the dam is impacting sediment distribution. Downstream effects are not shown to be significant. The output of this study also implies similar impacts at other drinking water storage impoundments. This research recommends that a sediment management plan be put in place for Altnahinch Dam and that further studies be carried-out concentrating on fine sediment distribution upstream of the dam.     

Geotechnical investigation of the El-Elb dam site,northwest Riyadh,Saudi Arabia,using 2D resistivity and ground-penetrating radar techniques

In the present study, the existence of cavities, voids, and fractures was verified at the site of the El-Elb Dam, which is located to the northwest of Riyadh City across Wadi Hanifa, using 2D electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) techniques. For this purpose, four ERT profiles were measured on the downstream side of the El-Elb Dam using the Syscal Pro Switch-72 resistivity meter. In addition, a GPR survey using a 400-MHz antenna and a SIR-3000 instrument was conducted along five profiles above the stilling basins on the downstream side of the dam and one radar profile was measured outside the stilling basins area across the course of the wadi. The resultant geophysical data were interpreted with the aid of information from a field-based structural and stratigraphic evaluation of the outcropped bedrock on the banks of the wadi course. The analysis of the inverted ERT and filtered radar sections revealed several resistivity and electromagnetic reflection anomalies that are identified laterally and vertically across the measured sections. These anomalies indicate the presence of fractures and karst features affected the limestone bedrock in the dam site. These near-surface karstified and fractured strata represent a critical hazard to the structural safety of the dam.     

江西九江武山铜矿构造-蚀变矿化特征及深部成矿预测

武山铜矿地处长江断裂南侧的九江—瑞昌构造带中心部位,发育于横立山—黄桥向斜的北翼。不整合面及武山岩体接触带是矿体赋存的主要部位;上泥盆统五通组含砾石英砂岩和中石炭统黄龙组白云质灰岩之间的层间断裂带、中石炭统黄龙组和下二叠统栖霞组灰岩的层间断裂带控制块状多金属硫化物体的成生与富集,而武山岩体与石炭系、二叠系灰岩、灰岩捕虏体的接触带则形成夕卡岩型矿体;在武山岩体和石英砂岩接触部位则难以形成工业矿体。在研究断裂构造、接触带构造、褶皱构造和围岩组成特征基础上,预测在标高-1 100 m之上,武山岩体与灰岩的接触带中仍有较好的找矿前景,而在武山岩体与泥盆系、志留系巨厚碎屑砂岩的接触部位则矿化较差。     

River water quality in weathered limestone: A case study in upper Mahanadi basin, India

Stromatolitic limestone and calcareous shale belonging to Chattisgarh Supergroup of Proterozoic age dominate the upper part of the Mahanadi river basin. X-ray diffractogram (XRD) of limestone rocks show presence of a significant amount of calcite, dolomite and ankerite. Shales of various colours contain calcite and dolomite. It is observed that congruent dissolution of carbonate minerals in the Charmuria pure limestone has given rise to a typical karst topography. On the other hand, limestones are also seen to support red and black soil profiles. This indicates that the limestone bedrock undergoes a parallel incongruent weathering, which leaves a residue of decomposed rock. The XRD analyses reveal that the limestone soils thus formed contain an assemblage of quartz, clays and Fe-oxides. It is likely that the silicate component trapped during deposition of the stromatolitic limestone weathers incongruently resulting in diverse soil profiles. Carbonate and silicate mineral weathering schemes have been worked out to explain the soil formation, fixation of Al in clay minerals, and Fe in goethite. The water quality parameters such as Ca, Mg and HCO₃ in the river water suggest under saturation with respect to calcite and dolomite. The mineral stability diagrams indicate that kaolinite and Ca-smectite are stable in the river water environment, hence they occur in suspended sediments and soils. The dominant influence of carbonate weathering on the water quality is observed even in the downstream part of the river outside the limestone terrain.     

Response times of salinity in relation to changes in freshwater inflows in the Lower Hillsborough River, Florida

The Lower Hillsborough River, Florida is a short (16 km) riverine estuary which has a dam located at its upstream end. Salinity below the dam is influenced by freshwater that flows over or through the structure. Depending on location in the estuary, the response of salinity to changes in upstream freshwater inflows is normally not instantaneous, but lags behind the freshwater release. An analytical approach and a laterally averaged two-dimensional hydrodynamic model were used to examine the response time of salinity in the Lower Hillsborough River to changes in freshwater inflows from the upstream reservoir. A series of case studies were conducted using the model to determine how salinity in the river within one kilometer below the dam would respond to changes in freshwater inflows. The model results suggest that the time lag of salinity in the river depends on whether the upstream freshwater inflows are increasing or decreasing, as well as their magnitude. While the time lag for salinity is about six to eight days for decreasing inflows, it is much shorter for increasing inflows depending on the magnitude of the flow release.     

Foraminiferal Biostratigraphy of the Mobarak Formation (Lower Carboniferous) in Kiyasar Area,SE Sari,Northern Iran

The Mobarak Formation is near the town of Kiyasar in the south-east of Sari city, northern Iran. This formation conformably overlies the Geirud Formation (Upper Devonian). The lower part of the Mobarak Formation consisting of shales and thin- to medium-bedded limestone toward the top of these sequences changes into alternations of dark limestone and interbedded gray to black shales. Weathered yellow thick-bedded shales are observed at the top of the section. This formation is covered unconformably by sandstones attributed to the Dorud Formation (Lower Permian). The thickness of the formation in this region is 250 m. Four rock units have been recognized in this section. Foraminiferal biostratigraphy shows that the age of the Mobarak Formation in the Kiaysar region ranges from Lower Tournaisian to Early Middle Visean. The foraminifer Zones FAZ1 and FAZ2 are correlated with the Lower Tournaisian and Upper Tournaisian, whereas Zones FAZ3 and FAZ4 correlate with the Visean. Affinities exist between specimens recorded in the Kiyasar section with species known from other regions in eastern and Central Alborz, but there are important differences in their appearance.     

Treatment of the seepage problems at the Kalecik Dam (Turkey)

This paper describes the seepage prevention measures at Kalecik Dam. Water leaked from the foundation of the dam after the impoundment. The dam, 77 m in height, was constructed for irrigation purposes.

The foundation consists of Mesozoic ophiolite, Paleocene allochthonous units composed of different lithologies and Miocene conglomerate. Karstified and fractured Paleocene limestone outcrops on the right bank of the dam foundation. This unit extends into, and its thickness increases within, the right abutment. The leakage occurs towards the downstream springs through the right bank limestone.

The main grout curtain is 200 m long and 60 m deep and was constructed on the right bank. After reservoir impounding, new springs were observed in the downstream area. Therefore, after the construction of the dam, remedial curtain grouting was required and carried out in three stages. Firstly, the main grout curtain was supplemented by additional grouting to seal the fractures and infill karstic cavities. The diversion tunnel was also repaired. The curtain depth was the same as the depth of the previous curtain. The second stage of additional treatment consisted of new deep grouting. Some investigation holes were also drilled along the same alignment as the main curtain to locate the seepage in the region. These holes were extended to an elevation of 442 m. The final stage of grouting measures was between the spillway and the dam body and underneath the spillway.

As a result of the additional grouting measures, the spring discharges observed downstream of the dam embankment decreased. However, the seepage paths were extended and were moved with time so that the seepage problems are still continuing.     

A late Middle Pleistocene temperate–periglacial–temperate sequence (Oxygen Isotope Stages 7–5e) near Marsworth, Buckinghamshire, UK

River-channel and colluvial deposits, near Marsworth, Buckinghamshire, record a temperate-periglacial-temperate sequence during the late Middle Pleistocene. The deposits of a lower channel contain tufa clasts bearing leaf impressions that include Acer sp., and Sorbus aucuparia and containing temperate arboreal pollen attributed to ash-dominated woodland. The tufa probably formed at the mouth of a limestone spring before being redeposited in a small river whose deposits contain plant remains, Mollusca, Coleoptera, Ostracoda and vertebrate bones of temperate affinities. The sediments, sedimentary structures and limited biological remains above the Lower Channel deposits indicate that fluvial deposition preceded climatic cooling into periglacial conditions. Fluvial deposition recurred during a later temperate episode, as shown by the mammalian bone assemblage in stratigraphically higher channel deposits. The Upper Channel deposits are confidently attributed to Oxygen Isotope Sub-Stage 5e (Ipswichian) on the basis of their vertebrate remains. However, the age of the Lower Channel deposits is less clear. The mammalian and coleopteran remains in the Lower Channel strongly suggest correlation with Oxygen Isotope Stage 7 on the basis of their similarities to other sites whose stratigraphy is better known and the clear difference of the Lower Channel assemblage from well-established faunas of Ipswichian or any other age. By contrast, U–Th dating of the tufa clasts suggests an age post 160 ka BP, while Aile/Ile ratios on Mollusca point to an Ipswichian age and younger. Four ways of interpreting this age discrepancy are considered, the preferred one correlating the Lower Channel deposits with Oxygen Isotope Stage 7.     

芦山地震冶勒大坝强震监测资料分析

冶勒沥青混凝土心墙堆石坝最大坝高为124.5 m,坝址区地震烈度高,地质条件复杂,两岸坝基条件严重不对称。大坝上布设了9台强震仪组成的强震监测台阵,曾获得2008年汶川地震和攀枝花地震的大坝强震监测记录。2013年4月20日四川省雅安市芦山县发生里氏7.0级地震,冶勒大坝距震中约212.5 km,坝址区震感较为强烈,强震监测台阵获得了此次地震较为完整的有效记录。对芦山地震主震记录进行时域分析和频谱分析,总结冶勒大坝在芦山地震中的动力反应规律,并与汶川地震时坝体动力反应进行对比分析。研究表明,芦山地震主震时冶勒大坝最大加速度记录为47.043 cm/s2,最长持续时间为76.98 s,坝顶动力放大效应明显;芦山和汶川地震时大坝动力反应规律的差异与地震波频谱特性及大坝自振特性等密切相关。总体而言,冶勒大坝在震后运行安全稳定,芦山地震未对冶勒大坝造成明显不利影响。     

蠕虫状灰岩特征和成因新探

下扬子地区下三叠统中广泛分布着一种外貌独特的灰岩——蠕虫状灰岩,这种灰岩出现在该区深水和浅水的多种环境中,具有灰泥结构和粒泥(或泥粒)结构;斜层理、生物扰动构造和压扁透镜状构造。蠕虫状灰岩是多成因的,各成因之间有着一定的联系,其中,先期形成的可被后期形成的叠加和改造。沉积作用、沉积分异作用是形成蠕虫状灰岩的一个重要前提,而生物扰动作用、水流作用和压实、压溶作用则是形成各种蠕虫状灰岩的关键。     

扬子北缘京山-钟祥地区下奥陶统地层序列及其区域对比

湖北京山-钟祥一带的下奥陶统特征与毗邻的峡东及随南地区存在明显差异,在此开展了岩石地层和生物地层研究对比有助于更好地了解扬子北缘早奥陶世的古地理特征及演化.通过详细的剖面测制和地层对比研究,将钟祥-京山地区下奥陶统自下而上分为娄山关组、温峡口组（新建）、钟祥组（新建）和大湾组.新建的温峡口组以竹叶状灰岩、鲕粒灰岩、生物碎屑灰岩为主,属于台地边缘浅滩-浅水陆棚相沉积.根据温峡口组中所产的腹足、腕足和头足类化石,认为其沉积时代为特马豆克期中-晚期至弗洛期早期.钟祥组为灰色-灰黑色笔石页岩夹薄层粉砂岩及少量生物碎屑灰岩透镜体,产丰富的腕足、三叶虫、海百合茎、笔石、头足类等生物化石,属于深水陆棚区沉积,其地质时代为早奥陶世弗洛期.通过区域地层对比,温峡口组与峡东南津关组、分乡组、红花园组和随南高家湾组底部层位相当,而钟祥组则与峡东大湾组下段的下部和随南高家湾组中-上部可以对比.      

柴达木盆地东北缘石炭系生物礁发育特征及其地质意义

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